Although the incidence of degenerative changes in the blood vessels is well known to increase with advancing age, quantitative data on the changes in peripheral blood flow due to the aging process per se are lacking. Venous occlusion plethysmography has been shown to be the most accurate and reproducible method to measure the peripheral blood flow. We used this method to evaluate peripheral blood flow in the subjects of the Baltimore Longitudinal Study of Aging (BLSA) with ages ranging from 20 to 83 years. The study was designed to evaluate the effect of age on peripheral blood flow by venous occlusion plethysmography at rest and in response to post-occlusion hyperemia and thermal stress, both of which result in near-maximal flow. Neither resting nor post-occlusion hyperemic blood flow as relate to age in these 146 BLSA men and women who underwent occlusions of 1, 2, and 3 minutes both at 26 degrees C and 35 degrees C. These results suggest that peripheral blood flow is not limited by age per se in man. In a second protocol, the response of peripheral blood flow to intravenvous infusion of isoproterenol and sodium nitroprusside was determined by plethysmography in 25 healthy volunteers ages 25-84 years.